Hypoplastic Left Ventricle or Hypoplastic Left Heart Syndrome (HLHS)

A rare form of congenital heart disease, hypoplastic left ventricle or hypoplastic left heart syndrome (HLHS) affects a small percentage of newborns in the U.S. Hypoplastic left heart syndrome is characterized by a combination of defects in the heart and surrounding blood vessels that happen when the left side of the heart isn’t fully formed in utero. The mitral valve, left ventricle (lower chamber), aorta and aortic valve may all be too small or absent. These parts of the heart are essential to delivering oxygenated blood to the body. Adding to the strain on the heart, a narrowing or coarctation of the aorta may also be present. With treatment and ongoing care by a pediatric cardiologist, children with hypoplastic left heart syndrome may be able to have an active life.

Wellness & Prevention

Hypoplastic left ventricle occurs during the first eight weeks of pregnancy as the heart’s four chambers develop from a hollow tube. After birth, the right side of the heart takes in oxygen-depleted blood from the body and pumps it to the lungs, then the left side pumps the oxygen-rich blood to the body. With HLHS, the right side of the heart has to work harder to pump blood to the body too.

Two natural holes in the heart that usually close after birth can help the heart compensate for hypoplastic left heart syndrome. Connecting the pulmonary artery and the aorta, the ductus arteriosus blood vessel lets oxygen-rich and oxygen-poor blood mix and sends some oxygenated blood into the aorta to carry to the body. The baby’s skin, lips and nails may begin to look blue because the mixed blood doesn’t contain enough oxygen.

The ductus arteriosus usually closes shortly after a baby is born but a pediatric cardiologist can prescribe medication to prevent the vessel from closing until a baby with hypoplastic left heart syndrome can have surgery or a heart transplant. If the ductus arteriosus closes, the baby may go into shock, suffer organ failure and congestive heart failure.

The second opening, called the foramen ovale, is in the wall between the atria and also allows blood to mix and flow into the right ventricle to be pumped to the lungs.

An infant with a hypoplastic left ventricle tends to exhibit symptoms shortly after birth. Symptoms may include:

  • Gray or blue skin tone
  • Poor feeding
  • Rapid or troubled breathing
  • Irritability
  • Enlarged liver
  • Tiredness
  • Circulatory collapse
  • Cold hands and feet

Hypoplastic left heart syndrome can be very serious and may require immediate treatment by a pediatric cardiologist.


Your obstetrician may be able to detect hypoplastic left ventricle with fetal echocardiography (ultrasound) before your baby is born. The test can be performed when the fetus is at least 16 weeks old. Once the baby has been born, your child’s doctor may notice signs of HLHS during a physical examination shortly after birth.

To confirm a diagnosis of hypoplastic left heart syndrome, a pediatric cardiologist may perform different tests including:

  • Chest X-ray: An X-ray produces an image that shows the size and shape of your baby’s heart and the lungs.
  • Electrocardiogram (ECG or EKG): Electrocardiograms measure the electrical activity in the heart through electrodes placed on your baby’s chest, arms and legs. An ECG can show abnormal rhythms and stress on the heart.
  • Echocardiogram: Using an ultrasound, an echocardiogram creates an image of the heart and assesses the structure and function, including information about how blood flows and how well the heart is pumping blood.


It’s important that hypoplastic left heart syndrome is treated immediately to protect your child’s health. Treatment can start as quickly as immediately after birth when babies with HLHS are given IV medications to stop the ductus arteriosus from closing. Your pediatric cardiologist may also prescribe medication to help dilate blood vessels. Another early treatment may involve using cardiac catheterization to widen the foramen ovale for better blood flow.

A child with HLHS will likely need three surgeries between the ages of 2 weeks and 4 years old to restore adequate function to the heart. In more severe cases, your pediatric cardiologist may recommend having a heart transplant.


Children with hypoplastic left heart syndrome typically need lifelong care from a cardiologist who can monitor their heart health and prescribe medication to regulate and improve heart function. As they grow older, children may need surgery to continue repairing the heart.

Some children with HLHS can lead active lives with no restrictions. Others may need to restrict their activities at the recommendation of their pediatric cardiologist.